Di-quaternary ammonium salts of α-1,4-thiazine alkanephosphonic acids as corrosion inhibitors

ABSTRACT

Use, as a corrosion inhibitor, of di-quaternary ammonium salts of α-1,4-thiazine alkanephosphonic acids.

This is a division, of application Ser. No. 932,259, filed Aug. 9, 1978,now U.S. Pat. No. 4,264,768 issued Apr. 28, 1981.

This invention relates to novel di-quaternary ammonium salts ofα-1,4-thiazine alkanephosphonic acids of the formula: ##STR1## where Ris a hydrocarbon or a substituted hydrocarbon group for example alkyl,alkenyl, cycloalkyl, aryl, aralkyl, substituted aryl, etc., the R's arehydrogen or a substituted group such as a hydrocarbon group, i.e.,alkyl, etc.; is a bridging group for example a hydrocarbon group such asalkylene, alkenylene, alkaralkylene or hydrocarbon groups alsocontaining other elements than carbon and hydrogen, Z is S, ##STR2## Mis hydrogen, or a salt moiety such as alkali metal, alkaline earthmetal, alkyl-ammonium, or ammonium and X is an anion such as halide,acetate, sulfonate, aralysulfonate, etc.; and to the preparation anduses thereof.

These compounds are prepared by reacting 2 mols of an α-1,4-thiazinealkanephosphonic acid compound with one mol of di-alkylating agent in asuitable polar solvent or a mixture of polar solvents. The preparationof α-1,4-thiazine alkanephosphonic acids is described in Ser. No.932,257 filed Aug. 9, 1978, now U.S. Pat. No. 4,264,767 issued Apr. 28,1981. The reaction may be illustrated by the following equation:##STR3##

Examples of the divinyl sulfur compounds include ##STR4##

Solvents useful in the method of this invention are water, mixtures ofwater and lower alcohols, lower alcohols, dimethyl formamide, dimethylsulfoxide, etc.

After combining the reactants in a suitable reactive medium, thereaction mixture is heated to from 50° C. to 150° C. with stirring topromote the alkylation reaction.

After the reaction is complete, the di-quaternary ammonium product maybe isolated or used as is in the practice of this invention.

The quaternary nitrogen are joined together by any suitable bridgingmeans, such as for example a hydrocarbon group such as alkylene,alkenylene, aryl group such as alkaryalkylene such as ##STR5## etc., orhydrocarbon group containing other than carbon and hydrogen, for examplealkyletheralkylene such as ##STR6##

X X may be a wide variety of polymerizing compounds, i.e., capable ofjoining amino groups, where may be alkylene, alkenylene, alkynylene,alkaralkylene, an alkyleneether-containing group, an ester-containinggroup, etc., and X is a halide.

The following are non-limiting examples: (I) Saturated dihalides

    X  X

where is alkylene, straight chain or branched, for example X(CH₂)_(n) Xwhere n is 2-25 or more, for example 2-10, but preferably 2-4. The

    -CH.sub.2).sub.n

may be branched such as where at least one of the H's is a hydrocarbongroup such as alkyl, i.e., methyl, ethyl, etc., substituted such ashalo, hydroxy, etc.

(II) Aralkylene dihalides

    X  X

where Z is aralkylene having for example 8-30 or more carbons, such as8-20 carbons, but preferably xylylene.

The following are illustrative examples: ##STR7##

Additional examples of aralkylene radicals include those of the formula--CH₂ --Ar--CH₂ -- where Ar is ##STR8##

(III) Alkylene ethers

    X--A--X

where A is an alkyleneether radical --A(OA)_(n) where A is alkylene(including cycloalkylene ether radicals) having for example from 1-10 ormore carbons such as 1-4, but preferably 2 in each alkylene unit.Typical examples are ##STR9##

Additional examples of A include groups of the formula (AO)_(n) where Ais ##STR10## where Y is alkyl, for example ##STR11## etc.

Thus, A can be methylene, polymethylene, ethylene, propylene, butylene,octylene, etc. In addition (AO)_(n) may be homo or hetero as to A, toyield for example (ETO)_(a) (PrO)_(b), (PrO)_(a) (BuO)_(b), or(PrO--ETO)_(n) ;

    --CH.sub.2 OCH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 OCH.sub.2 --

etc.

These compounds also include the formal of ethylene chlorohydrin andbromohydrin, for example

    ClCH.sub.2 CH.sub.2 OCH.sub.2 OCH.sub.2 CH.sub.2 Cl, ClCH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 OCH.sub.2 OCH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 CL

etc.

(IV) Unsaturated dihalides

    X  X

where is an unsaturated aliphatic radical, for example

    --CH.sub.2 --CH═CH--CH.sub.2 --

    --CH.sub.2 --C.tbd.C--CH.sub.2 --

etc.

The reaction is illustrated by the following examples.

EXAMPLE 1

Into a flask equipped with a mechanical stirrer, heating jacket, andreflux condenser are charged 48.6 g. (0.2 mol) of ##STR12## 21.6 g. (0.1mol) of 1,4-dibromobutane, 35 g. of water and 35 g. of 2-propanol. Thereaction mixture was heated to reflux and held there for 8 hours. Thereaction mixture was stripped of volatiles in vacuo. The resulting solidwas washed several times in methanol. It was recrystallized severaltimes from aqueous ethanol. The structure of the product was indicatedto be: ##STR13##

Anal. Calculated: N, 4.00; P, 8.83; Br, 22.79. Found: N, 3.85; P, 8.65;Br, 22.54.

EXAMPLE 2

Into a suitable reaction vessel were charged 51.4 g. (0.2 mol) of##STR14## 24.4 g. (0.1 mol) of 1,6-dibromohexane, 50 ml. of water and 50ml. of ethanol. The reaction mixture was heated to reflux and held therefor 8 hrs. The product was: ##STR15##

EXAMPLE 3

Into a suitable reaction vessel were charged 51.4 g. (0.2 mol) of##STR16## 12.5 g. (0.1 mol) of 1,4-dichlorobutene-2, 50 ml. of2-propanol and 25 ml. of water. The reaction mixture was heated toreflux and held there for 8 hrs. The product was: ##STR17##

Since the examples described herein are similarly prepared, they will bepresented in the following table.

    ______________________________________                                         ##STR18##                                                                    Example  R                           X                                        ______________________________________                                        4        CH.sub.3   (CH.sub.2).sub.6 Br                                       5        CH.sub.3                                                                                  ##STR19##       Cl                                                 ##STR20## (CH.sub.2).sub.4 Br                                       7        CH.sub.3   (CH.sub.2).sub.2 Br                                       8        C.sub.3 H.sub.7                                                                          (CH.sub.2).sub.4 Br                                       9        C.sub.3 H.sub.7                                                                          CH.sub.2 CHCH CH.sub.2                                                                         Cl                                       10       C.sub.11 H.sub.23                                                                        (CH.sub.2).sub.4 Br                                       11       C.sub.11 H.sub.23                                                                        CH.sub.2 CHCH CH.sub.2                                                                         Cl                                       12       C.sub.17 H.sub.33                                                                        (CH.sub.2).sub.4 Br                                       ______________________________________                                    

USE AS A SCALE INHIBITOR

Scale formation from aqueous solutions containing an oxide variety ofscale forming compounds, such as calcium, barium and magnesiumcarbonate, sulfate, silicate, oxalates, phosphates, hydroxides,fluorides and the like are inhibited by the use of threshold amounts ofthe compositions of this invention which are effective in small amounts,such as less than 2.5 p.p.m.

The compounds of the present invention (i.e., the acid form of thecompounds) may be readily converted into the corresponding alkali metal,ammonium or alkaline earth metal salts by replacing at least half of thehydrogen ions in the phosphonic acid group with the appropriate ions,such as the potassium ion or ammonium or with alkaline earth metal ionswhich may be converted into the corresponding sodium salt by theaddition of sodium hydroxide. If the pH of the amine compound isadjusted to 7.0 by the addition of caustic soda, about one half of the--OH radicals on the phosphorous atoms will be converted into the sodiumsalt form.

The scale inhibitors of the present invention illustrate improvedinhibiting effect at high temperatures when compared to prior artcompounds. The compounds of the present invention will inhibit thedeposition of scale-forming alkaline earth metal compounds on a surfacein contact with aqueous solution of the alkaline earth metal compoundsover a wide temperature range. Generally, the temperatures of theaqueous solution will be at least 40° F., although significantly lowertemperatures will often be encountered. The preferred temperature rangefor inhibition of scale deposition is from about 130° to about 350° F.The aqueous solutions or brines requiring treatment generally containabout 50 p.p.m. to about 50,000 p.p.m. of scale-forming salts. Thecompounds of the present invention effectively inhibit scale formationwhen present in an amount of from 0.1 to about 100 p.p.m., andpreferably 0.2 to 50 p.p.m. wherein the amounts of the inhibitor arebased upon the total aqueous system. There does not appear to be aconcentration below which the compounds of the present invention aretotally ineffective. A very small amount of the scale inhibitor iseffective to a correspondingly limited degree, and the threshold effectis obtained with less than 0.1 p.p.m. There is no reason to believe thatthis is the minimum effective concentration. The scale inhibitors of thepresent invention are effective in both brine, such as sea water, andacid solutions.

The following examples are presented to illustrate the use of thephosphonates prescribed herein and are presented for purposes ofillustration and not of limitation.

The following test was used to evaluate these compositions as scaleinhibitors.

Procedure:

1. Make up stock CaCl₂.2H₂ O,2.94 g/L or 56 g/5 gallons (18.9 liters)

2. Stock NaHCO₃ should be 3.35 g/L or 64 g/5 gallons.

3. Inhibitors--Make 0.1 percent solutions in deionized water. 1 ml in100 sample=10 p.p.m. (Test at 5, 20, and 50 p.p.m.).

Put 50 ml bicarbonate solution into 100 ml milk dilution bottle. Addinhibitor (for 100 ml final volume). Then add 50 ml CaCl₂ solution andset in bath at 180° F. Do not cap. Always prepare a blank. Run ahardness determination on a 50--50 mixture before heating.

Heat at 180° F. Take 10 ml samples from bottles after 2 hours and 4hours.

Filter through millipore filter.

run total hardness on filtrate.

Calculate as % Ca still in solution, i.e., ##EQU1##

The Compounds were tested at 180° F. at the concentrations indicated.Hardness readings were taken after 2 and 4 hours.

                  TABLE A                                                         ______________________________________                                        Scale Inhibitor Tests                                                                           Concen-    % Protec-                                        Compound          tration    tion                                             ______________________________________                                        Example 1          5 p.p.m.  30                                                                 50 p.p.m.  60                                               Example 1 (sodium salt)                                                                         50 p.p.m.  55                                               Example 2          5 p.p.m.  29                                                                 50 p.p.m.  58                                               Example 3 (sodium salt)                                                                          5 p.p.m.  31                                               Example 8 (sodium salt)                                                                          5 p.p.m.  30                                                                 50 p.p.m.  57                                               Typical Commercial                                                                               5 p.p.m.  24                                               Inhibitor         50 p.p.m.  30                                               ______________________________________                                    

USE IN THE CHELATION OR SEQUESTRATION OF METAL IONS

The chelating or sequestering agents of the present invention are ofwide utility such as when it becomes necessary to sequester or inhibitthe precipitation of metal cations from aqueous solutions. Among theirmany uses are the following applications:

Soaps and detergents, textile processing, metal cleaning and scaleremoval, metal finishing and plating, rubber and plastics industry, pulpand paper industry, oil well treatment, chelation in biological systems.

An important function of these compounds is their ability to sequesterFe⁺². In secondary oil recovery by means of water floods, waters arefrequently mixed on the surface prior to injection. Frequently thesewaters contain amounts of Fe⁺² and H₂ S. If these incompatible watersare mixed, an FeS precipitate results which can plug the sand face ofthe injection well. Another of their functions is to prevent formationof gelatinous iron hydroxides in the well and in the effluent productionwaters.

To demonstrate the effectiveness of the di-quaternary ammonium salts ofthe present invention in chelating Fe⁺², the following test procedurewas utilized. Into a flask that contained a known concentration of thesequestering agent, and enough sodium hydroxide or hydrochloric acid togive the desired pH was placed a 100 ml. aqueous sample of ferrousammonium sulfate (20 p.p.m. of Fe⁺²); after final pH adjustment thesolution was allowed to remain at ambient temperatures for 48 hours. Thesolution was centrifuged for one hour to remove colloidial ironhydroxide and an aliquot of the supernatant solution was analyzed byatomic absorption to determine the iron concentration.

The following table illustrates the ability of the sequestering agentsof the present invention to sequester Fe⁺², as compared to the wellknown sequestering agent tetra-sodium ethylenediamine tetra-acetate(EDTA).

                  TABLE I                                                         ______________________________________                                                                  Amount                                                                        of iron                                                       Sequestering    sequestered                                         pH        agent (p.p.m.)  (p.p.m.)                                            ______________________________________                                        5         Ex. 1 (50)      10                                                            Ex. 2 (50)      10                                                            EDTA (50)       7                                                   7         Ex. 1 (50)      10                                                            Ex. 3 (50)      9                                                             EDTA (50)       7                                                   10         Ex. 1 (150)    8                                                              Ex. 3 (150)    7                                                              EDTA (150)     6                                                   ______________________________________                                    

As one can observe from the preceding table, the sequestering agents ofthis invention are as effective, and in some cases superior, to EDTAwhen tested over a wide pH range.

The sequestering agents of this invention are also quite effective insequestering other metal cations in aqueous solutions. For example, atest was conducted in which 60 p.p.m. of the sequesterant were dissolvedin 100 ml. of water. The pH was adjusted to 9 and maintained there.Metal cations were added, in the following amounts, before a noticeableprecipitate was formed.

                  TABLE II                                                        ______________________________________                                                            Metal (p.p.m.)                                                                sequestered                                               Sequesterant,       per 60 p.p.m.                                             product of          sequesterant                                              ______________________________________                                        Example 1           Fe.sup.+3 (60)                                                                Al.sup.+3 (100)                                                               Cu.sup.+2 (100)                                                               Ni.sup.+2 (50)                                            Example 3           Fe.sup.+3 (60)                                                                Al.sup.+3 (100)                                                               Cu.sup.+2 (90)                                                                Ni.sup.+3 (50)                                            ______________________________________                                    

Other heavy metals sequestered by the sequestering agents of thisinvention such as cobalt, manganese, chromium and the like.

The amount employed to chelate is controlled by stoichiometry incontrast to scale inhibition where the amount employed is threshold orless than stoichiometric.

USE AS A MICROBIOCIDE

(I) In water treatment

This phase of the present invention relates to the treatment of water.More particularly, it is directed to providing improved means forcontrolling microbiological organisms including bacteria, fungi, algae,protozoa, and the like, present in water.

It is well known that ordinary water contains various bacteria, fungi,algae, protozoa and other microbiological organisms which, ifuncontrolled, multiply under certain conditions so as to present manyserious problems. For example, in swimming pools the growth of thesemicrobiological organisms is very undesirable from a sanitary standpointas well as for general appearances and maintenance. In industrial watersystems such as cooling towers, condenser boxes, spray condensers, watertanks, basins, gravel water filters, and the like, microbiologicalorganisms may interfere greatly with proper functioning of equipment andresult in poor heat transfer, clogging of systems and rotting of woodenequipment, as well as many other costly and deleterious effects.

In other industrial applications where water is used in processes, asfor example, as a carrying medium, etc., microbiological organisms mayalso constitute a problem in maintenance and operation. Illustrative ofsuch industrial applications are the pulp and paper manufacturingprocesses, oil well flooding operations and the like.

The products of this invention are suitable as biocides for industrial,agricultural and horticultural, military, hygienic and recreationalwater supplies. They provide an inexpensive, easily prepared group ofproducts which can be used, in minimal amounts, in water supplies, incooling towers, air-conditioning systems, on the farm and ranch, in thefactory, in civilian and military hospitals and dispensaries, in camps,for swimming pools, baths and aquaria, waterworks, wells, reservoirs, byfire-fighting agencies, on maritime and naval vessels, in boilers,steam-generators and locomotives, in pulp and paper mills, forirrigation and drainage, for sewage and waste disposal, in the textileindustry, in the chemical industries, in the tanning industry, etcetera, and which will render said water supplies bactericidal,fungicidal and algicidal. They further provide a simple process wherebywater supplies, for whatever purposes intended, are renderedbacteriostatic, fungistatic and algistatic, i.e., said water suppliestreated by the process of this invention will resist and inhibit thefurther growth or proliferation of bacteria, fungi, algae and all formsof microbial life therein.

(II) Water flooding in secondary recovery of oil

This phase of the present invention relates to secondary recovery of oilby water flooding operations and is more particularly concerned with animproved process for treating flood water and oil recovery therewith.More particularly this invention relates to a process of inhibitingbacterial growth in the recovery of oil from oil-bearing strata by meansof water flooding taking place in the presence of sulfate-reducingbacteria.

Water flooding is widely used in the petroleum industry to effectsecondary recovery of oil. By employing this process the yield of oilfrom a given field may be increased beyond the 20-30 percent of the oilin a producing formation that is usually recovered in the primaryprocess. In flooding operation, water is forced under pressure throughinjection wells into or under oil-bearing formations to displace the oiltherefrom to adjacent producing wells. The oil-water mixture is usuallypumped from the producing wells into a receiving tank where the water,separated from the oil, is siphoned off, and the oil then transferred tostorage tanks. It is desirable in carrying out this process to maintaina high rate of water injection with a minimum expenditure of energy. Anyimpediment to the free entry of water into oil bearing formationsseriously reduces the efficiency of the recovery operation.

The term "flood water" as herein employed is any water injected into oilbearing formations for the secondary recovery of oil. In conventionaloperations, the water employed varies from relatively pure spring waterto brine and is inclusive of water reclaimed from secondary recoveryoperations and processed for recycling. The problems arising from thewater employed depend in part on the water used. However, particularlytroublesome and common to all types of water are problems directly orindirectly concerned with the presence of microorganisms, such asbacteria, fungi and algae. Microorganisms may impede the free entry ofwater into oil-bearing formations by producing ions susceptible offorming precipitates, forming slime and/or existing in sufficiently highnumbers to constitute an appreciable mass, thereby plugging the pores ofthe oil-bearing formation. Free plugging increases the pressurenecessary to drive a given volume of water into an oil-bearing formationand oftentimes causes the flooding water to by-pass the formation to beflooded. In addition, microorganisms may bring about corrosion by actingon the metal structures of the wells involved, producing corrosivesubstances such as hydrogen sulfide, or producing conditions favorableto destructive corrosion such as decreasing the pH or producing oxygen.The products formed as the result of corrosive action may also bepore-plugging precipitates. Usually, the difficulties encountered are acombination of effects resulting from the activity of differentmicroorganisms.

(III) Hydrocarbon treatment

This phase of the present invention relates to the use of thesecompounds as biocides in hydrocarbon systems.

In addition to being used as biocides in aqueous systems, the compoundsof this invention can also be employed as biocides in hydrocarbonsystems, particularly when petroleum products are stored. It is believedthat bacteria and other organisms, which are introduced into hydrocarbonsystems by water, feed readily on hydrocarbons resulting in a loss inproduct; that microorganisms cause the formation of gums, H₂ S,peroxides, acids and slimes at the interface between water and oil; thatbacterial action is often more pronounced with rolling motion than understatic conditions, etc. Loss of product, corrosion of the storage tank,clogging of filters and metering instruments, and fuel deterioration areamong the harmful effects of bacteria growth in fuels. The activity ofmicroorganism growth is often increased by the presence of rust. Notonly do these microorganisms often encourage rust but rust encouragesmicroorganism growth. Since microorganism growth appears to beconsiderably higher with kerosene than with gasoline, plugged filtersexperienced with jet fuels which contain large amounts of kerosene is aserious problem.

The compositions of this invention can be employed in hydrocarbonsystems.

MICROBIOCIDAL TESTING

The screening procedure was as follows: a one percent by weight solutionof the test compound in water was prepared. The solution was asepticallyadded to a sterile broth that would support the growth of the testorganism, Desulfovibro desulfuricans, to provide the concentrationsindicated by weight of test compound per million parts by weight ofbroth. A general growth medium, such as prescribed by the AmericanPetroleum Institute was used. The broth containing the test compoundthen was dispersed in 5 cc. amounts into sterile disposable tubes andthe tubes were inoculated with the growing test organism and incubatedat 35° C. for 24 hours. The absence or presence of growth of themicroorganisms was determined by visual inspection by an experiencedobserver.

Following is a summary of the results of the testing of examples of thisinvention.

    ______________________________________                                        Compound      Concen-                                                         Example       tration                                                         Number        in p.p.m.   Results                                             ______________________________________                                         2 (Sodium salt)                                                                            75          *Gave control                                       10 (sodium salt)                                                                            25          "                                                   11 (sodium salt)                                                                            25          "                                                   ______________________________________                                         *By control is meant that the test compound was biostatic or biocidal         i.e., no growth of the test organism occurred under the test conditions. 

USE IN ACID SYSTEMS

The compounds of this invention can also be employed as corrosioninhibitors for acid systems, for example as illustrated by the picklingof ferrous metals, the treatment of calcareous earth formations, etc.,as described in the following sections.

USES

This invention also relates to the inhibition of corrosion, particularlythe corrosion of metals in contact with the acid solutions.

The present invention is especially useful in the acidizing or treatingof earth formations and wells traversed by a bore hole. It may also beused in metal cleaning and pickling baths which generally compriseaqueous solutios of inorganic acids such as sulfuric acid, hydrochloricacid, phosphoric acid and are useful in the cleaning and treatment ofiron, zinc, ferrous alloys, and the like.

If no corrosion inhibitor is present when the aqueous acidic solutioncomes in contact with the metal, excessive metal loss and consumption orloss of acid, and other adverse results will be experienced. There hasbeen a continuing search for corrosion inhibitors which can be usedeffectively in small concentrations, and which are economical toproduce. The need is also for corrosion inhibitors which are effectiveat high temperatures, e.g., 200° F. and above, such as are found inoperations involving acidic solutions, particularly oil-well acidizingwhere higher and higher temperatures are found as the well extendsfurther into the earth.

While the compounds of this invention are of themselves particularlygood acid corrosion inhibitors, optionally they may be blended withacetylenic alcohols, dispersing and solubilizing agents such asethoxylated phenols, alcohols, and fatty acids. They may also be blendedwith such known acid inhibitors as the quinoline or alkyl pyridinequaternary compounds or synergists such as terpene alcohols, formamide,formic acid, alkyl amine, alkylene polyamines, heterocyclic amines, andthe like.

Quaternary ammonium compounds may be illustrated by C-alkylpyridine-N-methyl chloride quaternary, C-alkyl pyridine-N-benzylchloride quaternary, quinoline-N-benzyl chloride quaternary,isoquinoline-N-benzyl chloride quaternary, thioalkyl pyridinequaternaries, thioquinoline quaternaries, benzoquinoline quaternaries,thiobenzoquinoline quaternaries, imidasole quaternaries, pyrimidinequaternaries, carbazole quaternaries, the corresponding ammoniumcompunds, pyridines and quinolines may also be used alone or incombination with the quaternary compounds. Thus a pyridine plusquinoline quaternary, a quinoline plus quinoline quaternary, orquinoline or amine alone or in combination may be used.

The formic acid compound may be selected from the esters and amides offormic acid. The formic acid compound may be from the group consistingof formate esters of the structure:

    HCOOR

where R is a monoaryl group, an alkyl group having 1 to 6 carbon atoms,cyclo-alkyl residues having 5 to 6 carbon atoms, alkenyl and alkynlgroups having 2 to 6 carbon atoms which may contain functional groupingsselected from --C--OH, --OH, ═C═O, --COOH, --SH, and NH₂. Examples ofthe formic acid compound are: methyl formate, ethylformate, benzylformate, other alkyl and aryl formates, and the like. Other examlesinclude formamide, dimethyl formamide, formanilide, and the like.Mixtures of the esters and mixtures of the amides may be used.

USE IN ACIDIZING EARTH FORMATIONS

The compositions of this invention can also be used as corrosioninhibitors in acidizing media employed in the treatment of deep wells toreverse the production of petroleum or gas therefrom and moreparticularly to an improved method of acidizing a calcareous ormagnesium oil-bearing formation.

It is well known that production of petroleum or gas from a limestone,dolomite, or other calcareous-magnesian formation can be stimulated byintroducing an acid into the producing well and forcing it into the oilor gas bearing formation. The treating acid, commonly a mineral acidsuch as HCl, is capable of forming water soluble salts upon contact withthe formation and is effective to increase the permeability thereof andaugment the flow of petroleum to the producing well.

CORROSION TEST PROCEDURE

In these tests the acid solutions were mixed by diluting concentratedhydrochloric acid with water to the desired concentrations.

Corrosion coupons of 1020 steel (AISI) were pickled in an uninhibited10% HCl solution for 10 minutes, neutralized in a 10% solution ofNaHCO₃, dipped in acetone to remove water and allowed to dry. They werethen weighed to the nearest milligram and stored in a desicator.

In most of the tests, a 25 cc/in² acid volume to coupon surface arearatio was used. After the desired amount of acid was poured into glassbottles, the inhibitor was added. The inhibited acid solution was thenplaced in a water bath which had been set at a predetermined temperatureand allowed to preheat for 20 minutes. After which time, the couponswere placed in the preheated inhibited acid solutions. The coupons wereleft in the acid solutions for the specified test time, then removed,neutralized, recleaned, rinsed, dipped in acetone, allowed to dry, thenreweighed.

The loss in weight in grams was multiplied times a calculated factor toconvert the loss in weight to lbs./ft² /24 hrs. The factor wascalculated as follows: ##EQU2##

    ______________________________________                                        CORROSION INHIBITION IN 15% HCl                                               Inhi-            Test     Test   Corrosion Rate                               bitor   p.p.m.   Temp.    Time   (lbs/ft.sup.2 /day)                          ______________________________________                                         2      2000     150° F.                                                                         4 hrs. 0.079                                        10      2000     150° F.                                                                         4 hrs. 0.050                                        12      2000     150° F.                                                                         4 hrs. 0.048                                        Blank            150° F.                                                                         4 hrs. 0.220                                        ______________________________________                                    

I claim:
 1. A process of inhibiting corrosion of metals exposed to acorrosive liquid medium which comprises adding to said corrosive liquidmedium an effective amount of a compund having the formula ##STR21##where R is alkyl, alkenyl, cycloalkyl, aryl, alkaryl, aralkyl orhydroxyphenyl, R' is hydrogen or alkyl, Z is S, SO or SO₂, M is hydrogenor a salt moiety, is a bridging group selected from alkylene,aralkylene, alkaralkylene, alkylene- or polyalkylene ether, alkenyleneor alkinylene and X is a halide.
 2. The process of claim 1 where thecorrosive liquid medium is an aqueous brine or acid.
 3. The process ofclaim 1 where R' is hydrogen and Z is SO₂.
 4. The process of claim 3where R is methyl, ethyl, pr hexyl, undecyl, heptadecyl, phenyl,hydroxyphenyl, tolyl, benzyl cyclohexyl and ##STR22##